Quantitative analysis of thermoluminescence signals of glass displays from mobile phones

Abstract

Glass displays from mobile phones show a characteristic thermoluminescence (TL) signal after the exposure to ionizing radiation. Therefore they can be used as accident and emergency dosimeters. This paper carries out quantitative analysis of such TL signals by using several standard methods of analyzing luminescence signals. Application of the initial rise method to 120 TL glow curves obtained by the Tmax-Tstop method, shows that the TL signals can be described by a quasi-continuous distribution of energies in the range of E=0.8-1.5 eV. The shape of the TL signals was simulated by using five Gaussian trap energy distributions centered at five discrete activation energy values and a single frequency factor s. The result of the simulations were in a good quantitative agreement with all the experimental TL glow curves. Two additional experiments investigating the variation of the TL signal with the heating rate, and studying the fading of the TL signal at room temperature over long periods of time, showed that this material exhibits the well known anomalous heating rate effect, and anomalous fading of the TL signal. The results of these two experiments demonstrate that the luminescence mechanism in this dosimetric material is rather complex, and that additional recombination pathways affect the luminescence process during a TL measurement.